Polycyclohexylenedimethylene terephthalate (PCT) is now receiving attention as a new material which can overcome the problem of polyester materials such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and so on, i.e., the problem that they have been only applied to restrictive uses because of their poor formability and low thermal deformation temperature due to slow crystallization rate.
The PCT is a crystalline polyester prepared by esterification reaction or trans-esterification reaction of terephthalic acid (hereinafter, ‘TPA’) or dimethyl terephthalate (hereinafter, ‘DMT’) and 1,4-cyclohexanedimethanol (hereinafter, ‘CHDM’), and has high melting point (Tm) and rapid crystallization rate. Since the PCT was first developed in the 1960s, it has been mainly used for carpets because of the characteristic soft feel of the PCT fiber but the use of the PCT has gradually decreased with the appearance of polyamide. Meanwhile, the PCT compound formulation was developed in the engineering plastic field in the 1980s and the PCT has been used for connectors and heat resistance parts in electrical and electronic industry field and automobile industry field requiring high heat resistance.
On the other hand, light emitting diode (LED) takes center stage with rapidly replacing a large number of existing light sources because of its excellent energy efficiency and lifespan. LED is generally composed of a semiconductor composing light emitting part, solder wires, a reflection plate, and a transparent encapsulant for encapsulating the semiconductor. Among them, the reflection plate was made of various materials, for example, ceramics or heat resistance plastics, but the ceramics had a problem in the productivity and the heat resistance plastics had a problem of falling-off in optical reflectivity because of variation in color in the process of preparing the reflection plate such as the injection molding process or the process for heat-curing the encapsulant or in the real usage environment condition of LED.
Particularly, since LED shows excellent energy efficiency and lifespan, high levels of reflectivity and heat resistance are required so that the reflection plate is used as LED parts and accessories, for example, the drop in the reflectivity after yellowing test of about 6,000 hrs at the reference temperatures such as about 25° C., about 55° C., about 85° C., or real LED operating temperature must be about 8% or less. Therefore, the studies about the materials which can maintain their high reflectivity even under severe conditions are needed.